I know this isn't the busiest of places for Aperture stuff, but some of the new AppleScript hooks in 2.1 are opening up a few possibilities, although some of them are similar to what's already possible with iView.

Basically, whenever you grab an Aperture Preview file via the media browser or any open file dialog, it contains a fingerprint in the IPTC Special Instructions field. The fingerprint is actually the internal ID for that Version in Aperture, allowing scripts to go back and show that file, or export as a TIFF and bring back into your layout app etc.